Processing of a CMP slurry for improved planarization of integrated circuit wafers

ABSTRACT

The disclosure is directed to a system that processes chemical mechanical planarization (CMP) slurries to reduce or eliminate large particles in the slurries, which can scratch integrated circuit wafers without substantially altering a percentage of solids in the CMP slurry by weight. In particular, the system breaks up particles of a CMP slurry using an intensifier pump system and a fluid processing device. The techniques have proven much more effective than conventional filtering techniques in reducing or eliminating scratches to integrated circuit wafers when a processed CMP slurry is used in a CMP process.

TECHNICAL FIELD

The invention relates to chemical mechanical planarization (CMP) and,more particularly, processing techniques for CMP slurries.

BACKGROUND

Chemical mechanical planarization (CMP) is commonly used during thefabrication of integrated circuit wafers, e.g., silicon wafers. Duringintegrated circuit wafer manufacture, CMP is typically used to make thesurface of the wafers both flat (i.e., planar) and smooth (i.e.,polished) by removing excess materials, such as copper or otherconductors or insulators, that are deposited and etched on theintegrated circuit wafer. CMP is typically performed multiple times,e.g., after each successive layer is applied in the formation of anintegrated circuit wafer.

In the CMP process, CMP slurries, which include hard particles in acarrier solution, may be deposited onto a rotating polishing pad. Theintegrated circuit wafer is then placed into contact with the polishingpad and typically rotates in the same direction as the polishing pad,but at a different rotational rate. The CMP slurries deposited onto thepolishing pad are used to polish and planarize the integrated circuitwafer as part of the fabrication process.

During the integrated circuit wafer fabrication process, several CMPsteps may be performed. Typically, each layer of the integrated circuitwafer may be fabricated using lithography, deposition, etching and thenCMP. After one layer is formed, the next layer is formed using similarprocesses. Unfortunately, CMP can sometimes introduce scratches into theintegrated circuit wafers. These scratches are highly undesirable andcan undermine the fabrication of integrated circuit wafers.

SUMMARY

In general, the invention is directed to a system that processeschemical mechanical planarization (CMP) slurries to reduce or eliminatelarge particles in the slurries, which can scratch integrated circuitwafers. In particular, the system breaks up particles of a CMP slurryusing an intensifier pump system and a fluid processing device. In thismanner, the system can reduce the number and size of large particlesthat otherwise exist in a CMP slurry without substantially altering apercentage of solids in the CMP slurry by weight. The techniques can bemore effective than conventional filtering techniques in reducing oreliminating scratches to integrated circuit wafers when processed CMPslurries are used in a CMP process.

In one embodiment, the invention provides a method comprising processinga CMP slurry via an intensifier pump system and a fluid processingdevice that breaks up at least some particles of the CMP slurry toreduce particle size. The method may further include planarizing anintegrated circuit wafer using the processed CMP slurry. Alternatively,the processed CMP slurry may itself be sold for use by another entity inplanarizing integrated circuit wafers.

In another embodiment, the invention provides a planarization system forintegrated circuit wafers comprising a CMP slurry processing system thatprocesses a CMP slurry to break up at least some particles of the CMPslurry to reduce particle size, and a CMP unit that planarizes anintegrated circuit wafer using the processed CMP slurry. In some cases,the CMP slurry processing system includes an intensifier pump system anda fluid processing device that breaks up at least some of the particlesof the CMP slurry. In this manner, the system can reduce the number andsize of large particles that otherwise exist in a CMP slurry.

The invention may provide one or more advantages. For example, theinvention may reduce the number and size of the large particle size tailin CMP slurries that cause scratches in integrated circuit wafers duringCMP without substantially altering a percentage of solids in the CMPslurry by weight. In this manner, the techniques can improve theefficiency and yield of integrated circuit wafer fabrication by reducingor eliminating such scratches. As noted above, the techniques describedin this disclosure may be more effective than conventional filteringtechniques in reducing or eliminating scratches to integrated circuitwafers when the processed CMP slurries are used in a CMP process.

In an added embodiment, the invention may comprise a chemical mechanicalplanarization (CMP) slurry comprising water, and particles dispersed inthe water. Substantially all of the particles have a diameter less thanapproximately 1 micron and the particles comprise at least one ofalumina (Al₂O₃), cerium oxide (CeO₂) and silicon dioxide (SiO₂).

Additional details of one or more embodiments are set forth in theaccompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of an exemplary system that can implementchemical mechanical planarization (CMP) slurry processing techniquesaccording to the invention.

FIG. 2 is a block diagram of an exemplary intensifier pump system thatmay be used according to the invention.

FIG. 3 is a cross-sectional side view of an exemplary fluid processingdevice that may be used according to the invention.

FIG. 4 is a cross-sectional side view of a portion of the fluidprocessing device shown in FIG. 3.

FIG. 5A is a simplified top view of a CMP unit that may be used toplanarize integrated circuit wafers according to the invention.

FIG. 5B is a simplified side view of the CMP unit shown in FIG. 5A.

FIG. 6 is a flow diagram illustrating a technique according to theinvention.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of an exemplary system 10 that can implementchemical mechanical planarization (CMP) slurry processing techniquesaccording to the invention. In accordance with the invention, system 10may incorporate a CMP slurry processing system 6, which breaks up atleast some particles of the CMP slurry to reduce particle size withoutsubstantially altering a percentage of solids in the CMP slurry byweight. In this manner, the system can reduce the number and size oflarge particles that otherwise exist in a CMP slurry. As described ingreater detail below, slurry processing system 6 may include anintensifier pump system 8, which uses two or more intensifier pumps thatoperate in a complementary fashion. In addition, slurry processingsystem 6 may include a fluid processing device 12 with opposing annularflow paths, as further described herein.

As shown in FIG. 1, a CMP slurry container 2 stores a CMP slurry(sometimes referred to as a “dispersion”). The slurry stored incontainer 2 may comprise any slurry commonly used for integrated circuitwafer planarization and polishing. For example, the slurry may compriseone or more types of hard particles in a carrier solution, such aswater. The hard particles may include one or more of alumina (Al₂O₃),cerium oxide (CeO₂), silicon dioxide (SiO₂), or other hard particlesused in CMP slurries. Following the processing described herein, thevast majority of particles (i.e., substantially all of the particles)exhibit a diameter of less than approximately 1 micron, which is highlydesirable to reduce or eliminate undesirable scratching during theplanarization process. In some cases, the CMP slurry may also includechemicals or additives, such as oxidizers, that can soften the materialto be removed during the planarization process and thereby help ensureconsistent removal rates during the planarization process.

One or more pumps 3 can serve to draw the CMP slurries from container 2and deliver the CMP slurries to a mixer 4. Mixer 4 is an optionalcomponent. Mixer 4 receives the CMP slurries pumped from container 2 andmixes the CMP slurries, e.g., to achieve uniform distribution of thehard particles in the carrier solution. Mixer 4 may comprise ahigh-shear mixer or the like, and is optional for system 10. Additionalmaterials, such as additives or the like, may also be added in one ormore stages using mixer 4 or additional mixers. Accordingly, CMP slurrycontainer 2 may or may not contain all of the ingredients of a final CMPslurry mixture.

As mentioned above, system 10 includes a CMP slurry processing system 6,which breaks up at least some particles in the CMP slurry to reduceparticle size to a size more desirable for the planarizationapplication. System 6 can do so without substantially altering apercentage of solids in the CMP slurry by weight. As shown in FIG. 1,slurry processing system 6 may include an intensifier pump system 8, anda fluid processing device 12.

Intensifier pump system 8 may include one or more intensifier pumps, andmay be capable of generating approximately 5,000 to 60,000 psi (34.5 MPato 413 MPa) of fluid pressure. Fluid processing device 12, as describedherein, may be capable of handling pressures greater than approximately10,000 psi (68,950 kPa), greater than approximately 30,000 psi (207MPa), greater than approximately 50,000 psi (345 MPa), or greater thanapproximately 60,000 psi (413 MPa). Following pressurization byintensifier pump system 8, the CMP slurry is delivered to fluidprocessing device 12. Fluid processing device 12 generates intense shearand extensional forces that reduces the size of the particles in the CMPslurry. In particular, fluid processing device 12 serves to break up anylarge particles of the CMP slurry into smaller-sized particles, andthereby produce a finely dispersed solution of particles in theprocessed CMP slurry having a more desirable size range withoutsubstantially altering a percentage of solids in the CMP slurry byweight. Heat exchangers (not shown) may be used to dissipate excessthermal energy generated during processing and generally control thetemperature of the processed slurry as desired. The shear andextensional forces are specifically useful in breaking up such largeparticles and may help to substantially eliminate any particles largerthan approximately 1 micron.

One or more filters 14 may also be used to filter particles from theprocessed CMP slurry. For example, filters 14 may comprise one or moreporous membranes, mesh screens, or the like, to filter the processed CMPslurry. Filters 14, however, are optional, and may be eliminated fromsome embodiments. In some cases, filtered portions of the processed CMPslurry (or, more generally, any unused portions of CMP slurry) may berecycled back to intensifier system 8 via a feedback loop 19.

The output of filters 14 (or the output of fluid processing device 12 iffilters 14 are not used) may then be delivered to a CMP unit 16. Ifdesired, a back pressure regulator (not shown) may be added downstreamof filters 14 to help maintain constant pressure in system 10 andprovide a return path to supply CMP slurry container 2.

CMP unit 16 planarizes and polishes an integrated circuit wafer usingthe processed CMP slurry. Since the CMP slurry is processed by CMPslurry processing system 6, scratches to the integrated circuit wafersmay be reduced in the processing stage relative to conventionaltechniques that rely solely on filtering to remove large particles fromthe CMP slurry. In particular, CMP slurry processing system 6 can reducethe number and size of large particles, such as particles larger than 1micron in diameter, by breaking up such particles into smaller moredesirable particle size without substantially altering a percentage ofsolids in the CMP slurry by weight. In some cases, such particles can becompletely eliminated.

CMP unit 16 may include a polishing pad and the processed CMP slurry maybe deposited onto the polishing pad. The polishing pad may rotate asanother mechanism rotates the integrated circuit wafer relative to therotating polishing pad in order to cause the integrated circuit wafer tobe planarized. This planarization step may be performed many times inthe fabrication of an integrated circuit wafer, e.g., with respect tomultiple different layers fabricated into the integrated circuit wafer.In some systems, multiple CMP units 16, all of which may be suppliedwith CMP slurries via the same CMP slurry processing system 6 describedherein.

FIG. 2 is a diagram of an exemplary intensifier system 8 in accordancewith an embodiment of the invention. Intensifier system 8 may beparticularly useful in the delivery of a continuous, steady, highpressure flow of CMP slurries to fluid processing device 12. Typicalfluid pressure may range from 0 psi to 40,000 psi (276,000 kilopascals),or greater, during each intensifier cycle. System 8 includes twodifferent intensifier pumps 80 and 85 that operate in a complementaryfashion to achieve the continuous, steady, high pressure flow of CMPslurries to fluid processing device 12. Additional intensifier pumps,however, could also be included in system 8. Also, a single intensifierpump could be used, but this embodiment might be less effective inachieving continuous, steady, high pressure.

Intensifier system 8 may be a hydraulic system that includes a lowpressure supply pump 15. Supply pump 15 is used to deliver a CMP slurryinto intensifier system 8 from a supply or reservoir (not shown in FIG.2). Supply pump 15 may be a diaphragm pump, or other suitable pump,capable of delivering an appropriate volume of the CMP slurry. Supplypump 15 may deliver the CMP slurry at about 60-100 psi, although thiscan vary from system to system. Referring back to FIG. 1, in analternative configuration, supply pump 15 (FIG. 2) could be used as pump3 (FIG. 1) with intensifier system 8 (FIG. 1) including the remainingcomponents of FIG. 2. In that case, mixer 4 (FIG. 1) could beeliminated, or possibly included after supply pump 15 (FIG. 2).

Referring again to FIG. 2, supply pump 15 feeds into inlet 20 of a checkvalve, hereinafter referred to as a “smart” valve 25. Smart valve 25 maycomprise a controllable valve that can be actively opened and closed bya controller 30. Smart valve 25 may include a valve poppet (not shown)that is coupled to an actuator (not shown) that is, in turn, coupled toair cylinder 35. Air cylinder 35 (or another type of actuator) iscontrolled by controller 30 and can quickly and efficiently open orclose smart valve 25 through the actuation of the valve poppet.

When smart valve 25 is opened, a CMP slurry is delivered throughinlet/outlet 40 of a charge intensifier pump 45. More specifically, theCMP slurry is delivered into an intensifier barrel 50. Chargeintensifier pump 45 includes a hydraulic actuator 55 having a hydraulicpiston 60. As hydraulic piston 60 is caused to move back and forth, itcauses product intensifier piston 65 to move back and forth as well.More specifically, as hydraulic piston 60 and product intensifier piston65 retract, the CMP slurry is able to fill intensifier barrel 50. Ashydraulic piston 60 advances, product intensifier piston 65 advances andthe CMP slurry is expelled through inlet/outlet 40 at the appropriateintensified pressure. Hydraulic piston 60 is caused to advance byintroducing hydraulic fluid under pressure through hydraulic fluidsupply inlet (advance) 52 and retracted by introducing hydraulic fluidunder pressure through hydraulic fluid supply inlet (retract) 54. AnLVDT 70 (linear variable displacement transducer) or other type ofposition sensor can be coupled with hydraulic piston 60 so as to providean indication of the piston's position to controller 30. Thus,controller 30 causes smart valve 25 to open when hydraulic piston 60 isready to begin its retraction cycle.

Each time supply intensifier piston 65 advances, the CMP slurry is movedthrough inlet/outlet 40 at a relatively high pressure into supply line75. While actual pressures will vary depending upon the configuration ofthe system, in one embodiment the CMP slurry enters the supply line atbetween 700-2000 psi (4830-13,800 Kilo Pascals). The CMP slurry is thendelivered to either a first product intensifier pump 80 or a secondproduct intensifier pump 85 (each of which has the same components inthe same configuration). It should be noted that more productintensifier pumps could be incorporated into the system and theillustrated embodiment having two such pumps is for illustrativepurposes only. Also, in simpler embodiments, an intensifier system couldinclude a single intensifier pump, although this would typically notprovide continuous, steady, high pressure.

As illustrated in FIG. 2, first product intensifier pump 80 is in aretracted position when second product intensifier pump 85 is at or nearthe end of an extension cycle. In this manner, first and second productintensifier pumps 80, 85 operate at least partially out of phase withone another to provide a combined output that is substantiallycontinuous and constant. Put another way, first and second productintensifier pumps 80, 85 operate in a complementary fashion, with oneproviding pressure intensification of a CMP slurry while the otherre-fills with the CMP slurry.

Second product intensifier pump 85 includes a hydraulic actuator 90having a hydraulic piston 95. Hydraulic piston 95 is coupled to aproduct intensifier piston 100 located within an intensifier barrel 105.A linear position transmitter (LPT) 110 is coupled between hydraulicpiston 95 and a controller 115 so as to provide positional informationto controller 115. Controller 115 may be coupled with an air cylinder120 or other type of actuator that actuates smart valve 125.

As hydraulic piston 95 reaches the end of its extension cycle,information indicative of this position is sent by LPT 110 to controller115. Controller 115 then causes smart valve 125 to open. The CMP slurryenters inlet 130 of smart valve 125, passes through and enters an inlet135 of intensifier barrel 105. Because the CMP slurry may be deliveredat pressures of about 1200 psi (8270 kilopascals) by charge intensifierpump 45, product intensifier piston 100 is forced backwards (inretraction) at a relatively high speed, also forcing hydraulic piston 95to retract. This eliminates the need to provide a mechanism tohydraulically retract piston 95, such as a hydraulic fluid inlet. LPT110 registers when hydraulic piston 95 has fully retracted and this datais passed to controller 115.

Charge intensifier pump 45 has a larger product displacement per strokethan that of second product intensifier pump 85. Thus, chargeintensifier pump 45 fully fills intensifier barrel 105 with each stroke.Furthermore, charge intensifier pump 45 fills intensifier barrel 105without introducing air, thus aiding in the control and elimination ofpulsation. Controller 115 can be configured to not immediately closesmart valve 125. Instead, smart valve 125 may remain open for apredetermined period of time to permit preloading. The CMP slurrycontinues to be delivered by charge intensifier pump 45, thus raisingthe pressure within intensifier barrel 105. In one embodiment, thepressure within intensifier barrel 105 is caused to increase to between1600-1700 psi (11,000-11,700 kilopascals). At the appropriate time,controller 115 then causes smart valve 125 to close.

Hydraulic fluid supply 140 is then caused to deliver hydraulic fluidunder pressure into hydraulic actuator 90. This, in turn, causeshydraulic piston 95 to advance, which causes product intensifier piston100 to advance. Normally, there would be a pre-compression phase wherethe CMP slurry within intensifier barrel 105 is caused to increase inpressure before it is expelled. However, this phase can be greatlyreduced or eliminated by bringing this CMP slurry to high pressure viathe charge intensifier pump 45. Of course, the desired output pressurewill be determinative of whether the pressures achieved by chargeintensifier pump 45 are sufficient for preloading. As productintensifier piston 100 advances, it forces the CMP slurry through outlet145 and causes check valve 150 to open. At the same time, smart valves125, 126 prevent backflow of the CMP slurry through fluid line 75. TheCMP slurry is then delivered, at pressure, to output line 155 where itbecomes intensified product outflow 160. At this point, the CMP slurryadvanced into fluid processing device 12, which is discussed in greaterdetail below. In one embodiment, product intensifier pumps 80, 85 candeliver the CMP slurry at pressures up to or exceeding 40,000 psi(276,000 kilopascals).

As product intensifier piston 100 reaches the end of its extensioncycle, smart valve 125 is again opened and the process in repeated.Likewise, the same process occurs with first product intensifier pump80. Specifically, like product intensifier pump 85, first productintensifier pump 80 includes a hydraulic actuator 91 having a hydraulicpiston 96. Hydraulic piston 96 is coupled to a product intensifierpiston 101 located within an intensifier barrel 106. A linear positiontransmitter (LPT) 111 is coupled between hydraulic piston 96 and acontroller 116 so as to provide positional information to controller116. LPT 111 may be located anywhere along hydraulic piston 96 orintensifier piston 101. Controller 116 is coupled with an air cylinder121 that actuates smart valve 126.

As hydraulic piston 96 reaches the end of its extension cycle,information indicative of this position is sent by LPT 111 to controller116. Controller 116 then causes smart valve 126 to open. The CMP slurryenters inlet 131 of smart valve 126, passes through and enters an inletof intensifier barrel 106. Because the CMP slurry may be delivered atpressures of about 1200 psi (depending upon the actual configuration ofthe system) by charge intensifier pump 45, product intensifier piston101 is rapidly forced backwards (in retraction), also forcing hydraulicpiston 96 to retract. LPT 111 registers when hydraulic piston 96 hasfully retracted and this data is passed to controller 116. This is theposition illustrated in FIG. 2.

Hydraulic fluid supply 141 is then caused to deliver hydraulic fluidunder pressure into hydraulic actuator 91. This, in turn, causeshydraulic piston 96 to advance which causes product intensifier piston101 to advance. As product intensifier piston 101 advances, it forcesthe CMP slurry through outlet 146 and causes check valve 151 to open.The CMP slurry is then delivered, at pressure, to output line 155 whereit becomes intensified product outflow 160. At this point, the CMPslurry is then delivered to fluid processing device 12. Thus, firstproduct intensifier pump 80 and second product intensifier pump 85 areconfigured so that one is always delivering product while the other isretracting. In this manner, substantially consistent and uniformintensified product outflow 160 is achieved without significant pressurepulses.

FIG. 3 is a cross-sectional view of an exemplary fluid processing device12 suitable for use in CMP processing system 6 of the larger system 10described above. Fluid processing device 12 may be capable of handlingpressures up to or greater than approximately 60,000 psi (413 MPa). Asdescribed herein, fluid processing device 12 receives a highlypressurized CMP slurry from intensifier system 8. The CMP slurry isseparated into two separate initial flow paths 225, 226. Flow paths 225and 226 feed into opposing sides of flow path cylinder 230, whichdefines annular flow paths.

In particular, the inner diameter of flow path cylinder 230 defines anouter diameter of annular flow paths that feed toward one another tomeet at the center of cylinder 230. Rod 232 is positioned inside flowpath cylinder 230. For example, rod 232 may define first and secondends. A first end of rod 232 extends into annular flow path 233 and asecond end of rod 232 extends into second annular flow path 234. Theouter diameter of rod 232 defines the inner diameter of the annular flowpaths. Accordingly, flow paths 225 and 226 respectively feed intoannular flow paths 233, 234 defined by flow path cylinder 230 and rod232.

The CMP slurry flows down annular flow paths 233, 234 and collides at ornear outlet 236 formed in flow path cylinder 230, e.g., approximately atthe lateral center of cylinder 230. The shear forces, extensionalforces, and impact forces of the collision of the CMP slurry flowingdown the annular flow paths 233, 234 causes particles in the CMP slurryto be broken into smaller, more desirable sized particles. Moreover,annular flow paths 233, 234 may enhance wall shear forces in fluidprocessing device 12 by increasing surface area associated with the flowpaths. In this manner, fluid processing device 12 can be used togenerate intense shear and extensional forces that act on the particlesin a CMP slurry. After processing, the CMP slurry is expelled throughoutlet 236 and exits fluid processing device 12 (as indicated at output238).

As further shown in FIG. 3, fluid processing device 12 may includepressure sensors 241, 242 to measure pressure within fluid processingdevice 12, as well as temperature sensors 243, 244 to measure the inputtemperature of the CMP slurry. A controller (not shown) may receive thepressure and temperature measurements, and adjust the pressure via oneor more regulator valves (not shown) to maintain a desired pressurewithin fluid processing device 12. Similarly, one of the controllersassociated with the intensifiers may receive temperature measurements,and cause adjustment of the temperature of the CMP slurry, as needed, tomaintain a desired input temperature for the CMP slurry into fluidprocessing device 12. In particular, it is generally desirable tomaintain substantially identical CMP slurry flows down the respectiveannular flow paths 233, 234 to ensure the desired impingement energydissipation.

Substantially identical flows of the CMP slurries down the respectiveannular flow paths 233, 234, e.g., in terms of pressure or temperature,is indicative of a non-clogged condition. Temperature monitoring, inparticular, can be used to identify when a clogged condition occurs, andmay be used to identify when an anti-clogging measure should be taken,e.g., application of a pulsated short term pressure increase in theinput flow to clear the clog.

Gland nuts 247, 248 may be used to secure flow path cylinder 230 in theproper location within fluid processing device 12. Moreover, gland nuts247, 248 can be formed with channels (indicated by the dotted lines)that allow fluid to flow freely through flow paths 225, 226 and intoannular flow paths 233, 234.

Rod 232 may be cylindrically shaped. However, other shapes of rod 232may further enhance wall shear forces in the annular flow paths. Rod 232may be free to move and vibrate within the flow path cylinder 230. Inparticular, rod 232 may be unsupported within flow path cylinder 230.Free movement of rod 232 relative to flow path cylinder 230 can providean automatic anti-clogging mechanism to fluid processing device 12. Ifparticles in the CMP slurry become clogged inside the fluid processingdevice 12, e.g., at the edges of annular flow paths 233, 234, rod 232may respond to local pressure imbalances by moving or vibrating. Inother words, a clog within cylinder 230 or in proximity of annular flowpaths 233, 234 may result in a local pressure imbalance that causes rod232 to move or vibrate. The movement and/or vibration of the rod 232, inturn, may help to clear the clog and return the pressure balance withinfluid processing device 12. In this manner, allowing rod 232 to be freeto move and vibrate within the flow path cylinder 230 can facilitateautomatic clog removal.

To further improve clog removal, a pulsated short term pressure increasein the input flow can be performed upon identifying a clog. For example,as mentioned above, temperature sensors 243, 244 may identifytemperature changes in flow paths 225, 226, which may be indicative of aclogged condition. In response, a short term pressure increase, e.g., atwo-fold pressure increase for approximately five seconds, can causemore substantial movement and/or vibration of the rod 232 to facilitateclog removal. The pulsated short term pressure increase in the inputflow can be performed in response to identifying a clogged condition, oron a periodic basis. For example, intensifier pump system 8 (FIG. 2) canbe used to adjust the input pressure to fluid processing device 12. Ashort term pressure increase may be particularly useful in clearingclogs that affect both annular flow paths 233, 234. In that case, thetemperature of both input flow paths may be similar, but may increasebecause of the clog that affects both annular flow paths 233, 234.

The components of fluid processing device 12, including flow pathcylinder 230 and rod 232 may be formed of a hard durable material suchas stainless steel or a carbide material. As one example, flow pathcylinder 230 and rod 232 can be formed of tungsten carbide containingapproximately six percent tungsten by weight. As another example, flowpath cylinder 230 and rod 232 may comprise so-called “non-corroding”stainless steel that will not corrode in the presence of an aqueous CMPslurry, such as 316 or 304 stainless steel.

FIG. 4 is a cross-sectional side view of a portion of a fluid processingdevice 12 that incorporates annular flow paths. Gland nuts 247, 248 maybe used to secure flow path cylinder 230 in the proper location withinfluid processing device 12. Moreover, gland nuts 247, 248 can be formedwith channels (indicated by the dotted lines) that allow fluid to flowfreely into annular flow paths 233, 234. The ends of flow path cylinder230 may be formed to mate with gland nuts 247, 248 in order tofacilitate securing of cylinder 230 in a precise location.

Again, annular flow paths 233, 234 are defined by flow path cylinder 230and rod 232. Flow path cylinder 230 may define a minimum width thatremains substantially constant along the annular flow paths. Rod 232 maybe cylindrically shaped, and can be free to move and vibrate within theflow path cylinder 230. Ordinarily rod 232 is concentric with theannular flow paths, having a center axis that is aligned with thecentral longitudinal axis of flow path cylinder 230. Fluid dynamicforces and uniform balance of rod 232 can force rod 232 toward thelateral and longitudinal center of the annular flow path. Movement andvibration of rod 232 within the flow path cylinder 230 can facilitateautomatic clog removal.

The minimum width of the inner diameter of flow path cylinder 230 may bein the range of approximately 0.1 inch (0.254 cm) to 0.001 inch (0.00254cm). For example, the width of the inner diameter of flow path cylinder230 may be approximately 0.0290 inch (0.07366 cm). The width of theouter diameter of rod 232 may be slightly smaller than the minimum innerdiameter of flow path cylinder 230. For example, if the width of theinner diameter of flow path cylinder 230 is approximately 0.0290 inch(0.07366 cm), the width of the outer diameter of rod 232 may be betweenapproximately 0.0260 inch (0.06604 cm) and 0.0280 inch (0.07112 cm).Other sizes, widths and shapes of flow path cylinder 230 and rod 232could also be used in accordance with the invention.

By way of example, the width of outlet 236 may be approximately between0.0001 inch (0.000254 cm) and 0.1 inch (0.254 cm). As one example, thewidth of outlet. 236 at the outer diameter of flow path cylinder 230 isapproximately between 0.006 inch (0.01524 cm) and 0.010 inch (0.0254cm). Outlet 236 may extend approximately 180 degrees around cylinder230, or may extend to a lesser or greater extent, if desired. Othersizes and shapes of outlet 236 could also be used.

FIGS. 5A and 5B are simplified top and side views, respectively, of aCMP unit 16 that may be used to planarize an integrated circuit wafer304 according to the invention. Notably, CMP slurry 305 includesparticles that have reduced particle sizes relative to conventionalslurries, due to the CMP slurry processing performed by CMP slurryprocessing system 6. The sizes of particles in CMP slurry 305 shown inFIG. 5A are greatly exaggerated for illustrative purposes. As noted, CMPslurry 305, processed as described herein, may have substantially allparticles with diameters less than approximately 1 microns.

CMP unit 16 includes a polishing pad 302 which rotates. Polishing pad302 may comprise a polyurethane material or the like. As polishing pad302 rotates, CMP slurry 305 is deposited onto polishing pad 302. Amechanism 306 holds an integrated circuit wafer 304, such as a siliconwafer, and lowers a surface of integrated circuit wafer 304 into contactwith polishing pad 302. Integrated circuit wafer 304 is rotated,typically in the same direction as polishing pad 302, but at a differentrotational rate. As shown, integrated circuit wafer 304 has a muchsmaller circumference than polishing pad 302 and is placed at an offsetlocation relative to the center of polishing pad 302. As polishing pad302 rotates, the CMP slurry 305 passes between co-rotating integratedcircuit wafer 304 and pad 302 to planarize and polish integrated circuitwafer 304 and remove excess materials that have been previouslydeposited onto integrated circuit wafer 304, e.g., to define circuittraces. The processing of CMP slurry 305, as described herein, can helpto reduce or eliminate scratches to integrated circuit wafer 304 duringthe process shown in FIGS. 5A and 5B.

The planarization/polishing shown in FIGS. 5A and 5B may be repeated forseveral successive layers of integrated circuit wafer 304. Each layer,for example, may be formed by lithography, deposition, etching and thenthe polishing/planarization shown in FIGS. 5A and 5B, which usesprocessed CMP slurry 305. Successive layers of integrated circuit wafer304 may be formed in similar successive fashion to form the finalintegrated circuit wafer, including many integrated layers of e.g.,silicon transistors, circuit traces and other circuit components.

FIG. 6 is an exemplary flow diagram illustrating a method for processinga chemical mechanical planarization (CMP) slurry via an intensifier pumpsystem and a fluid processing device that breaks up large particles inthe CMP slurry in order to reduce the number and size of undesirablelarge particles without substantially altering a percentage of solids inthe CMP slurry by weight. As shown in FIG. 6, pump 3 delivers a CMPslurry from container 2 to CMP slurry processing system 6 (401). Mixer 4(shown in FIG. 1) is optional.

In CMP slurry processing system 6, intensifier system 8 intensifies thepressure of the CMP slurry (402). Fluid processing device 12 breaks upparticles in the CMP slurry in order to reduce particle size (403),which can help minimize or reduce scratching to integrated circuitwafers. Following the processing by CMP slurry processing system 6, theprocessed CMP slurry is used in CMP unit 16 to planarize an integratedcircuit wafer (404).

EXAMPLE

Slurries: Commercially available alumina based first-step copper slurry(C-100), silica based copper first step slurry (C-002), ceria basedShallow Trench Isolation (STI) slurry (S-001), fumed silica based STIslurry (S-002), colloidal silica based copper barrier slurry (B-001),and fumed silica based copper barrier slurry (B-002) were used directlywithout any chemical alternation. A given slurry was fed through anintensifier pump system (like that illustrated in FIG. 2) and a fluidprocessing device (like that illustrated in FIG. 3), and the slurry wasimmediately directed onto a polishing pad without performing anyfiltration. The particle size and size distribution before and after thetreatment by intensifier pump and fluid processing device were measuredon a Matec Applied Sciences APS-100 Acoustic Particle Sizer. Theoversized particle count was measured on a Particle Sizing SystemsAccuSizer™ 780A.

Testing wafers: 8″ copper blanket wafers with 15000 A° PVD (PhysicalVapor Deposition) deposited copper on a stack comprising 250 A°tantalum, 5000 A° thermal oxide and a silicon substrate were used in theinvestigation. Patterned wafers from SKW company of Germany (6-3patterned wafers with 10,500 A° electroplated copper over 1000 A° copperseed layer) were deposited on SiO₂ trenches 5000 A° deep with 250 A°Ta/TaN as barrier was used. The SKW 6-3 wafers had features ranging from100 μm to 0.18 μm with varying pattern-densities.

Wafer planarization: All wafers were planarized using the slurriesmentioned above on a Strasbaugh n-Hance polisher equipped with Rohm HaasIC 1000™ pad and System Marshall Girt 100 pad conditioner. The slurryflow was set at 200 mL/min. The table/carrier speeds were set at 75/65rpm. The thickness on the Cu wafers was measured using the RS-35resistivity mapping tool. Measurements were carried out on twodiametrically perpendicular directions before and after planarization tocalculate the material removal rate (MRR) and the so called Within WaferNon-Uniformity (WIWNU). The surface quality of the planarized wafers wasexamined under the Burleigh Horizon Optical profilometer. The filmthickness of all non-metal wafers was measured using Filmetric opticalreflectometer. For patterned wafers, step-heights, dishing and erosionvalues were measured using Ambios XP-2 profilometer. PlanarizationEfficiency (PE) was calculated for the first step of the planarizationprocess. The defectivity count was conducted on a KLA-Tencor 7700MInspection Station with an optical microscope for defect classification.The post CMP clean before defectivity inspection was conducted on a SSSTEvergreen brush cleaner.

Results: Typical experimental results showed 30-70 percent reduction inlarge particle size (i.e., diameters>0.64 microns) counts in processedCMP slurries relative to unprocessed CMP slurries. Using the processingtechniques described above, an approximately 25% reduction in the volumeof particles in the large particle size tail of the CMP slurry wasachieved. Most importantly, significant scratch reductions were observedin integrated circuit wafers that were polished/planarized usingprocessed CMP slurries, relative to circuit wafers that werepolished/planarized using control unprocessed CMP slurries. Thissignificant reduction in scratches occurred without a significant changein MRR (Material Removal Rate).

A number of embodiments of the invention have been described.Nevertheless, it is understood that various modifications may be madewithout departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

1. A method comprising processing a chemical mechanical planarization(CMP) slurry via an intensifier pump system and a fluid processingdevice that breaks up at least some particles of the CMP slurry toreduce particle size.
 2. The method of claim 1, wherein the processingdoes not substantially alter a percentage of solids in the CMP slurry byweight.
 3. The method of claim 1, further comprising planarizing anintegrated circuit wafer using the processed CMP slurry.
 4. The methodof claim 3, wherein planarizing the integrated circuit wafer includesseveral separate planarizing steps.
 5. The method of claim 3, whereinplanarizing the integrated circuit wafer includes depositing theprocessed CMP slurry onto a polishing pad.
 6. The method of claim 5,wherein the polishing pad rotates and wherein planarizing the integratedcircuit wafer includes rotating the integrated circuit wafer relative tothe rotating polishing pad.
 7. The method of claim 3, further comprisingfiltering the processed CMP slurry prior to planarizing the integratedcircuit wafer.
 8. The method of claim 1, wherein the intensifier pumpsystem includes at least two hydraulic intensifier pumps, and whereinprocessing the CMP slurry includes operating the hydraulic intensifierpumps in a complementary fashion.
 9. The method of claim 1, wherein thefluid processing device includes: a first annular flow path for the CMPslurry; a second annular flow path for the CMP slurry; an outlet for theCMP slurry flowing within the first and second annular flow paths; aflow path cylinder that defines an outer diameter of the first andsecond annular flow paths, the outlet being formed in the flow pathcylinder; and a cylindrical rod positioned within the flow path cylinderthat defines an inner diameter of the first and second annular flowpaths, wherein the cylindrical rod is not attached to any structurewithin the fluid processing device and is free to move under fluiddynamic force relative to the flow path cylinder.
 10. The method ofclaim 1, wherein the CMP slurry includes particles dispersed in water.11. The method of claim 10, wherein the particles comprise at least oneof: alumina (Al₂O₃); cerium oxide (CeO₂) and silicon dioxide (SiO₂). 12.The method of claim 1, further comprising adding additives to the CMPslurry.
 13. A planarization system for integrated circuit waferscomprising: a chemical mechanical planarization (CMP) slurry processingsystem that processes a CMP slurry to break up at least some particlesof the CMP slurry to reduce particle size; and a CMP unit thatplanarizes an integrated circuit wafer using the processed CMP slurry.14. The planarization system of claim 13, wherein the CMP slurryprocessing system does not substantially alter a percentage of solids inthe CMP slurry by weight.
 15. The planarization system of claim 14,wherein the CMP slurry processing system includes an intensifier pumpsystem and a fluid processing device that breaks up at least some of theparticles of the CMP slurry.
 16. The planarization system of claim 15,wherein the intensifier pump system includes at least two hydraulicintensifier pumps that operate in a complementary fashion.
 17. Theplanarization system of claim 16, wherein the fluid processing deviceincludes: a first annular flow path for the CMP slurry; a second annularflow path for the CMP slurry; an outlet for the CMP slurry flowingwithin the first and second annular flow paths; a flow path cylinderthat defines an outer diameter of the first and second annular flowpaths, the outlet being formed in the flow path cylinder; and acylindrical rod positioned within the flow path cylinder that defines aninner diameter of the first and second annular flow paths, wherein thecylindrical rod is not attached to any structure within the fluidprocessing device and is free to move under fluid dynamic force relativeto the flow path cylinder.
 18. The planarization system of claim 14,wherein the CMP unit includes a polishing pad and wherein the processedCMP slurry is deposited onto the polishing pad.
 19. The planarizationsystem of claim 18, wherein the polishing pad rotates and wherein amechanism rotates the integrated circuit wafer relative to the rotatingpolishing pad.
 20. The planarization system of claim 14, wherein the CMPslurry includes particles dispersed in water, wherein the particlescomprise at least one of: alumina (Al₂O₃); cerium oxide (CeO₂) andsilicon dioxide (SiO₂).
 21. The planarization system of claim 14,further comprising one or more filters to filter the processed CMPslurry prior to planarizing the integrated circuit wafer.
 22. Theplanarization system of claim 14, further comprising a feedback loop tofeed unused portions of the processed CMP slurry back to the CMP slurryprocessing system.
 23. A chemical mechanical planarization (CMP) slurrycomprising: water; and particles dispersed in the water, whereinsubstantially all of the particles have a diameter less thanapproximately 1 micron and wherein the particles comprise at least oneof: alumina (Al₂O₃); cerium oxide (CeO₂) and silicon dioxide (SiO₂).